Assigning channels of different capacities in a hybrid ISDN-DECT telecommunications system

ABSTRACT

To allocate telecommunication channels of different channel capacity, e.g. the ISDN D channel and DECT channels to one another (e.g. simulation of the ISDN channel structure by the DECT channel structure) with good (economic) utilization of the bandwidth and minimum technical complexity in a hybrid telecommunication system, particularly an &#34;ISDN &lt;CUSTOM-CHARACTER FILE=&#34;US06175738-20010116-P00900.TIF&#34; ID=&#34;CUSTOM-CHARACTER-00001&#34;&gt; DECT-specific RLL/WLL&#34; system, a DECT-specific Cs channel and a DECT-specific Cf channel are used in dependence on the amount of information transmitted on the ISDN D channel for transmitting information in the hybrid telecommunication system.

BACKGROUND OF THE INVENTION

In communication systems comprising an information transmission linkbetween an information source and an information sink, transmitting andreceiving devices are used for information processing and transmission,in which devices

1) the information processing and information transmission can takeplace in a preferred direction of transmission (simplex mode) or in bothdirections of transmission (duplex mode),

2) the information processing is analog or digital,

3) the information transmission over the long-distance transmission linkis wire-connected or takes place wirelessly on the basis of various FDMA(Frequency Division Multiple Access), TDMA (Time Division MultipleAccess) and/or CDMA (Code Division Multiple Access) informationtransmission methods—e.g. according to radio standards such as DECT,GSM, WACS or PACS, IS-54, PHS, PDC etc. [Compare IEEE CommunicationsMagazine, January 1995, pages 50 to 57; D. D. Falconer et al.: “TimeDivision Multiple Access Methods for Wireless Personal Communications”].

“Information” is a generic term which stands both for the intelligence(information) and for the physical representation (signal). Even if aninformation contains the same intelligence—i.e. has the same informationcontent—different signal forms can occur. Thus, for example, aninformation relating to an object, can be transmitted

(1) in the form of an image,

(2) as a spoken word,

(3) as a written word,

(4) as a coded word or image.

In this connection, the type of transmission according to (1) . . . (3)is normally characterized by continuous (analog) signals whilstdiscontinuous signals (e.g. pulses, digital signals) are usuallyproduced in the case of the type of transmission according to (4).

Based on this general definition of a communication system, theinvention relates to methods for allocating telecommunication channelsof different channel capacity in a hybrid telecommunication system,particularly an “ISDN DECT-specific RLL (Radio Local Loop)/WLL (WirelessLocal Loop)” system according to the precharacterizing clause of claim1.

Hybrid telecommunication systems are, for example, communication systemscontaining different—wireless and/or wire-connected—telecommunicationsubsystems.

FIG. 1 shows—representative for the multiplicity of hybridtelecommunication systems—on the basis of the printed documents“Nachrichtentechnik Elektronik, Berlin 45 (1995) Vol. 1, pages 21 to 23and Vol. 3 pages 29 and 30” and IEE Colloquium 1993, 173; (1993), pages29/1-29/7; W. Hing, F. Halsall: “Cordless access to the ISDN basic rateservice” on the basis of a DECT/ISDN Intermediate System DIIS accordingto ETSI Publication prETS 300xxx, Version 1.10, September 1996, an “ISDNDECT-specific RLL/WLL” telecommunication system IDRW-TS (IntegratedServices Digital Network Radio in the Local Loop/Wireless in the LocalLoop) with an ISDN telecommunication subsystem I-TTS [compare printeddocument “Nachrichtentechnik Elektronik, Berlin 41-43, Part: 1 to 10,P1: (1991) Vol. 3, pages 99 to 102; P2: (1991) Vol. 4, pages 138 to 143;P3: (1991) Vol. 5, pages 179 to 182 and Vol. 6, pages 219 to 220; P4:(1991) Vol. 6, pages 220 to 222 and (1992) Vol. 1, pages 19 to 20; P5:(1992) Vol. 2, pages 59 to 62 and (1992) Vol. 3, pages 99 to 102; P6:(1992) Vol. 4, pages 150 to 153; P7: (1992) Vol. 6, pages 238 to 241;P8: (1993) Vol. 1, pages 29 to 33; P9: (1993) Vol. 2, pages 95 to 97 and(1993) Vol. 3, pages 129 to 135; P10: (1993) Vol. 4, pages 187 to 190”]and a DECT-specific RLL/WLL telecommunication subsystem RW-TTS.

In this arrangement, the DECT/ISDN intermediate system DIIS and,respectively, the RLL/WLL telecommunication subsystem RW-TTS arepreferably based on a DECT (Digital Enhanced (previously European)cordless telecommunication)/GAP system DGS; compare (1):Nachrichtentechnik Elektronik 42 (1992) January/February No. 1, Berlin,DE; U. Pilger “Struktur des DECT-Standards” (Structure of the DECTstandard), pages 23 to 29 in conjunction with ETSI Publication ETS300175-1 . . . 9, October 1992; (2): Telcom Report 16 (1993), No. 1, J.H. Koch: “Digitaler Komfort f{umlaut over (u)}r schnurloseTelekommunikation DECT-Standard eröffnet neue Nutzungsgebiete” (Digitalcomfort for cordless telecommunicationDECT standard opens up new fieldsof application), pages 26 and 27; (3): tec 2/93—The technical magazineby Ascom “Wege zur universellen mobilen Telekommunikation” (Approachesto universal mobile telecommunication), pages 35 to 42; (4): PhilipsTelecommunication Review Vol. 49, No. 3, September 1991, R. J. Mulder:“DECT, a universal cordless access system”; (5): WO 93/21719 (FIGS. 1 to3 and associated description)]. The GAP (Generic Access Profile)standard is a subset of the DECT standard which has the task of ensuringthe interoperability of the DECT air interface for telephoneapplications (compare ETSI Publication-prETS 300444, April 1995).

As an alternative, the DECT/ISDN intermediate system DIIS and,respectively the RLL/WLL telecommunication subsystem RW-TTS, can also bebased on a GSM system (Groupe Sp{acute over (e)}ciale Mobile or GlobalSystem for Mobile Communication; compare Informatik Spektrum 14 (1991)June, No. 3, Berlin, DE; A. Mann: “Der GSM-Standard—Grundlage f{umlautover (u)}r digitale europ{umlaut over (a)}ische Mobilfunknetze” (The GSMstandard—basis for digital European mobile radio networks), pages 137 to152). In the context of a hybrid telecommunication system it is alsopossible, instead, for the ISDN telecommunication subsystem I-TTS to beconstructed as a GSM system.

In addition, further possibilities to be considered for implementing theDECT/ISDN intermediate system DIIS and, respectively, the RLL/WLLtelecommunication subsystem RW-TTS or the ISDN telecommunicationsubsystem I-TTS are the systems mentioned initially, and future systemswhich are based on the known multiple-access methods FDMA, TDMA, CDMA(Frequency Division Multiple Access, Time Division Multiple Access, CodeDivision Multiple Access) and hybrid multiple-access methods formed fromthese.

The use of radio channels (e.g. DECT channels) in traditionalline-connected telecommunication systems such as the ISDN is gainingincreasing significance, particularly against the background of futurealternative network operators without their own complete wire-linenetwork.

Thus, it is intended to provide the ISDN subscriber with ISDN servicesat standard ISDN interfaces by means of the wireless RLL/WLL (Radio inthe Local Loop/Wireless in the Local Loop) line interfacing technique,e.g. including the DECT system DS, for example in the RLL/WLLtelecommunication subsystem RW-TTS (compare FIG. 1).

In the “ISDN DECT-specific RLL/WLL” telecommunication system IDRW-TSaccording to FIG. 1, a telecommunication subscriber (user) TCU(Telecommunication User) with his terminal equipment TE (also TerminalEndpoint) is tied in, e.g. via a standardized S interface (S-BUS), thepreferably DECT-specific DECT/ISDN intermediate system DIIS (firsttelecommunication subsystem) contained in the RLL/WLL telecommunicationsubsystem RW-TTS and constructed as local information transmission loop,a further standardized S interface (S-BUS), a network termination NT anda standardized U interface of the ISDN telecommunication subsystem I-TTS(second telecommunication subsystem) into the ISDN world and all theservices available therein.

The first telecommunication subsystem DIIS essentially consists of twotelecommunication interfaces, a first telecommunication interface DIFS(DECT Intermediate Fixed System) and a second telecommunicationinterface DIPS (DECT Intermediate Portable System) which are connectedto one another wirelessly, e.g. via a DECT air interface. Because of thequasi-stationary first telecommunication interface DIFS, the firsttelecommunication subsystem DIIS forms the local informationtransmission loop defined above in this connection. The firsttelecommunication interface DIFS contains a radio fixed part RFP, aninterworking unit IWUI and an interface circuit INC1 to the S interface.The second telecommunication interface DIPS contains a radio portablepart RPP and an interworking unit IWU2 and-an interface circuit INC2 tothe S interface. In this arrangement, the radio fixed part RFP and theradio portable part RPP form the known DECTIGAP system DGS.

For a DECT-specific RLL system as bearer for all ISDN services, ifpossible, in the subscriber loop, the following general problems aregiven:

a) Simulation of the ISDN channel structure (D channel and 2B-channels), especially of the D channel in the text which follows,

b) good economy of bandwidths; particularly significant for ISDN sincesome services already need two. DECT channels for the B-channel datarate of 64 kb/s,

c) minimum technical complexity.

Simulation of the D channel

Properties of the D channel:

Common signalling channel on the C plane for all terminal endpoints TEconnected to the ISDN line.

The TE-specific signalling channels to the network are separated thereby TE-individual addresses TEI (Terminal Endpoint Identifiers).

The order of information items is ensured TE-individually by the accessmechanism to -the. D channel.

Throughput: 16 kb/s

Usage: depends on many criteria, as a rule lower than maximum capacity;congestion situations are possible but can be rapidly cleared because ofthe high capacity.

DECT channels:

FIG. 2 shows the TDMA structure of the DECT/GAP system TKS in accordancewith the printed document “Nachrichtentechnik Elektronik 42 (1992)January/February, No. 1, Berlin, DE; U. Pilger: “Struktur desDECT-Standards” (Structure of the DECT standard), pages 23 to 29 inconjunction with ETS 300 175-1 . . . 9, October 1992”. With respect tothe multiple-access methods, the DECT/GAP system is a hybrid system inwhich radio messages can be sent on ten frequencies in the frequencyband between 1.88 and 1.90 GHz according to the FDMA principle within apredetermined time sequence according to the TDMA principle according toFIG. 2 from the base station RFP to the mobile part RPP and from themobile part RPP to the base station RFP (duplex mode). The time sequenceis determined by a multi-timeframe MZR which occurs every 160 ms andwhich has 16 timeframes ZR having in each case a duration of 10 ms.Within this timeframe ZR, information relating to a C, M, N, P, Qchannel defined in the DECT standard is transmitted separately from thebase station RFP and the mobile part RPP. If information for several ofthese channels is transmitted within one timeframe ZR, the transmissiontakes place in accordance with a list of priorities, where M>C>N andP>N. Each of the 16 timeframes ZR of the multi-timeframe MZR is, inturn, subdivided into 24 time slots ZS having in each case a duration of417 μs, out of which 12 time slots ZS (time slots 0 . . . 11) areintended for the “base station RFP→mobile part RPP” direction oftransmission and a further 12 time slots ZS (time slots 12 . . . 23) areintended for the “mobile part RPP→base station RFP” direction oftransmission. In each of these time slots ZS, information items having abit length of 480 bits are transmitted in accordance with the DECTstandard. Of these 480 bits, 32 bits are transmitted as synchronizationinformation in a SYNC field and 388 bits are transmitted as userinformation in a D field. The remaining 60 bits are transmitted asadditional information in a Z field and as guard information in a “guardtime” field. The 388 bits of the D field, transmitted as userinformation, are, in turn, subdivided into a 64-bit-long A field, a320-bit-long B field and a 4-bit-long “X-CRC” word. The 64-bit-long Afield is composed of a header with a length of 8 bits, a data recordwith data for the C, Q, M, N, P channels with a length of 40 bits and an“A-CRC” word with a length of 16 bits.

Properties:

Use of TDMA time slots.

In principle, one C_(s) channel (s=slow) is used per time slot forsignalling [C plane in the DECT standard] and an associated channel isused for the user information [U plane in the DECT standard] (32 kb/sthroughput).

Throughput of the C_(s) channel: 2 kb/s.

The DECT standard also offers other channel structures, e.g. a C_(f)channel (f=fast).

The C_(f) channel occupies one time slot.

Throughput of the C_(f) channel: 25.6 kb/B.

Based on the OSI/ISO reference model [compare (1): Unterrichtsbl{umlautover (a)}tter (Training sheets) Deutsche Telecom Vol. 48, 2/1995, pages102 to 111; (2): ETSI Publication ETS 300175- 1 . . . 9, October 1992;(3): ETSI Publication ETS 300102, February 1992; (4): ETSI PublicationETS 300125, September 1991; (5): ETSI Publication ETS 300012, April1992], FIG. 3 shows a model of the C plane of the “ISDN DECT-specificRLL/WLL” telecommunication system IDRW-TS according to FIG. 1.

Based on the OSI/ISO reference model [compare (1): Unterrichtsbl{umlautover (a)}tter (Training sheets) Deutsche Telecom Vol. 48, 2/1995, pages102 to 111; (2): ETSI Publication ETS 300175-1 . . . 9, October 1992;(3): ETSI Publication ETS 300102, February 1992; (4): ETSI PublicationETS 300125, September 1991; (5): ETSI Publication ETS 300012, April199], FIG. 4 shows a model of the U plane for voice data transmission ofthe “ISDN DECT-specific RLL/WLL” telecommunication system IDRW-TSaccording to FIG. 1.

Economy of bandwidths

The C_(s) channel structure offers optimum economy of bandwidths for astandard voice connection since, according to FIG. 5, on the basis ofFIGS. 3 and 4 and taking into consideration the ETSI Publications (ETS300175-1, 10/1992, Section 7; ETS 300175-3, October 1992, Section 4.1;ETS 300175-4, October 1992, Section 4), only one transmission path(bearer)—e.g. MBC with the LCNy, LCN1 according to FIG. 5—or,respectively, one connection or one time slot is needed.

According to FIG. 5, on the basis of FIGS. 3 and 4 and taking intoconsideration the ETSI Publications (ETS 300175-1, October 1992, Section7; ETS 300175-3, 10/1992, Section 4.1; ETS 300175-4, October 1992,Section 4), the use of the C_(f) channel leads to less economy ofbandwidths since the U plane itself-needs a further transmission path(bearer) or, respectively, a further connection or a further time slot;i.e. two bearers—e.g. MBC with the LCN2, LCNZ and MBC with the LCNy,LCN1 according to FIG. 5—or, respectively, two connections or two timeslots are needed for a simple voice connection.

Moreover, three bearers—e.g. MBC with the LCNx, LCN0, MBC with the LCNy,LCN1 and MBC with the LCNz, LCN2 according to FIG. 5—or, respectively,three connections or three time slots are required in the case wherethere are two ISDN B-channel connections (voice connections).

Although it appears to be appropriate to use the C_(f) channel from thepoint of view of channel capacity, the use of the C_(s) channel isappropriate from the point of view of economy of bandwidths.

Independently of whether it is the C_(f) channel or the C_(s) channelwhich is used for setting up the connection (setting up bearers), itmust be ensured (compare FIG. 5), that it is possible to change from theC_(f) channel to the C_(s) channel and conversely at any time (changingchannels between channels of unequal channel capacity). In addition, itmust be ensured that it is possible to change between a first C_(s)channel and a second C_(s) channel (changing channels between twochannels of equal channel capacity) because of the possibility that twoconnections (bearers) can be set up at the same time in the ISDN system(2 B-channels).

Technical complexity

The DECT-specific RLL system must appear to be transparent to the ISDNsubscriber and the ISDN network. For its internal functions such as, forexample, DECT channel selection etc., it needs control criteria whichmust be determined by the analysis of ISDN “Layer-2/Layer-3” messages(compare printed document “Nachrichtentechnik Elektronik, Berlin 45, P2:(1991) Vol. 4, pages 138 to 143”) of the network—ISDN subscriber(Terminal Endpoint TE) signalling if they are not explicitly availableat the network interfaces.

To minimize the complexity, it is possible to concentrate this body ofcontrol criteria in a telecommunication interface of thetelecommunication interfaces DIFS, DIPS, e.g. of the firsttelecommunication interface DIFS (DECT Intermediate Fixed System) and tocontrol the other telecommunication interface in each case, in thepresent case the second telecommunication interface DIPS (DECTIntermediate Portable System) from there. In this constellation, thefixed system DIFS is always able to select a DECT channel structurecorresponding to the ISDN service (C plane and U plane).

In the portable system DIPS, this is not possible without direct accessto the ISDN layer 3. It is not able to map a TE-individual connectionwith C and U plane unambiguously onto a corresponding DECT channelstructure from the ISDN layer 2 function alone in all situations.

Even if this were possible, there remains the problem of the differencein throughput when only the C_(s) channel is used, which is economicwith respect to bandwidths.

An approach is therefore sought which, with good economy of bandwidthsand low system complexity, maps the entire D channel of an ISDN lineonto a DECT channel arrangement in such a manner that the fundamentalproperties of the D channel are not changed and situations of congestioncan be rapidly relieved.

A known design for the standardization of such a system has hithertoprovided for the use of the C_(f) channel for as long as the ISDN lineis active. The central control function lies in the fixed system DIFSwhich controls the portable system DIPS via the C_(f) channel. Thissolution is relatively simple but has the disadvantage, that the economyof bandwidths is not optimum.

SUMMARY OF THE INVENTION

The object forming the basis of the invention consists in allocatingtelecommunication channels of different channel capacity, e.g. the ISDND channel and DECT channels to one another (e.g. simulation of the ISDNchannel structure by the DECT channel structure) with good (economic)utilization of the bandwidth and minimum technical complexity in ahybrid telecommunication system, particularly an ISDN DECT-specificRLL/WLL system.

The basic concept of the invention consists in using the DECT-specificC_(s) channel and the DECT-specific C_(f) channel for the informationtransmission in a hybrid telecommunication system in dependence on theamount of information transmitted in the ISDN D channel. In thisarrangement, it is especially the technical facts with respect to theobject forming the basis of the invention, which have been discussed inthe introduction to the description for hybrid telecommunicationsystems, particularly a ISDN DECT-specific RLL/WLL system, which arebeing taken into consideration.

The aim of the solution is a dynamic adaptability of the capacity of aDECT channel arrangement carrying the D channel to the currentthroughput -demand of the D channel whilst largely retaining theproperties of the known draft standard explained in the introduction tothe description.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel,are set forth with particularity in the appended claims. The invention,together with further objects and advantages, may best be understood byreference to the following description taken in conjunction with theaccompanying drawings, in the several Figures of which like referencenumerals identify like elements, and in which:

FIG. 1 depicts a prior art telecommunication system;

FIG. 2 depicts a TDMA structure of the FIG. 1 system;

FIG. 3 depicts a model of the C plane of the FIG. 1 system;

FIG. 4 depicts a model of the U plane for voice data transmission of theFIG. 1 system;

FIG. 5 depicts channel structure of the FIG. 1 system;

FIG. 6 depicts a configuration of transmitting and receiving sectionsaccording to the present invention;

FIGS. 7-10 depict channel changes according to the present invention;and

FIGS. 11-15 depict signal flow in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 6 shows, on the basis of FIGS. 1 to 5, the basic configuration of atransmitting section and receiving section in each case for the firsttelecommunication interface DIFS and the second telecommunicationinterface DIPS, which is of significance for the analysis of the ISDN“layer-2/layer-3” messages and, respectively, the amount of informationtransmitted via these (compare printed document “NachrichtentechnikElektronik, Berlin 41, P2: (1991) Vol. 4, pages 138 to 143”) on the“ISDN network ISDN subscriber (Terminal Endpoint TE) transmission link.

In the transmitting section of the first telecommunication interfaceDIFS and, respectively, the second telecommunication interface DIPS, theNWK layer (Network Layer) transfers ISDN “layer-2/layer-3” informationand DECT control information in familiar manner via a first queue WSD,constructed as a buffer, to the DLC (Data Link Control) layer. A MAC/DLCcontroller STE of the transmitting section measures the loading ratio inthe queue WSD and stimulates from this the MAC (Medium Access Control)layer and DLC layer. As long as the loading ratio remains below athreshold SD, the DLC layer deposits the information (message) to betransmitted in a second queue WSS, also constructed as a buffer, fromwhich it transmits the MAC layer on the C_(s) channel to the receivingsection.

When the threshold SD is exceeded, the DLC layer deposits theinformation in a third queue WSF, again constructed as a buffer, fromwhich it transmits the MAC layer to the receiving section on a C_(f)channel which is set up for this purpose. The C_(s) channel is usedagain when the first queue WSD and the third queue WSF are empty.

From the transmitting section and/or the receiving section, e.g. thefirst telecommunication interface DIFS and/or the secondtelecommunication interface DIPS detect(s) the necessity of producing achange of channel (change from one subsystem channel to anothersubsystem channel). The stimulus for the change of channel is formed bythe result of the analysis. The configuration of the transmittingsection and receiving section shown in FIG. 6 can thus be used forcontrolling the change of channel.

For the resultant change of channel between the C_(s) channel and theC_(f) channel, it is supposed that the C_(s) channel C_(f) channelassociation in the first telecommunication interface DIFS and the secondtelecommunication interface DIPS is known, using the DECT standard. Likethe C_(s) channel, naturally, the C_(f) channel can also be used fortransmission in the opposite direction if it already exists.

FIGS. 7 to 10 show a first illustrative embodiment for the change ofchannel.

The operation in detail

As long as the loading ratio of the first queue WSD is below thethreshold SD, the DLC layer uses the DECT A-field format (DECT standard)for feeding the second queue WSS. After the threshold SD has beenexceeded, the third queue WSF is fed in the DECT B-field format.Switching over to transmitting from the third queue WSF is done afterthe C_(f) channel has been set up, when the second queue WSS is empty orthe C_(f) channel is ready.

There are two possibilities for changing from the A format to the Bformat:

a) The queue WSS only contains complete A-field DLC frames:

Then, switching over is always done at DLC frame boundaries. There arethree criteria for dimensioning the DLC frames:

shortest possible frames so that the delay of switching over totransmitting from the third queue WSF remains as short as possible,

on the other hand, the DLC PDU (Protocol Data Unit) data overhead riseswhen the maximum DLC frame length is not utilized,

bridging the set-up time for the C_(f) channel.

To control the C_(s) channel C_(f) channel switch-over, DLC (Data LinkControl) procedures are used.

Thus, e.g., the standard DECT procedures “Class B acknowledgedsuspension/Class B resumption” are used in modified form specificallyfor this application (compare DECT standard ETS 300175-4, October 1992,Section 9.2.7).

C_(s) channel—C_(f) channel according to FIG. 7

When the first queue WSS is empty, i.e. the last I frame has beenacknowledged in accordance with the HDLC protocol, the initiatingtelecommunication interface DIFS, DIPS (e.g. the secondtelecommunication interface DIPS) sends a “SUSPEND” command on the C_(s)channel. If the other station (the first telecommunication interfaceDIFS) itself still has I frames to send from the first queue WSS, itwill terminate this as early as possible at the next frame boundary(remaining frames will be transferred to the third queue WSF), wait forthe last acknowledgement on the C_(s) channel and then accept the“SUSPEND” command on the C_(s) channel.

After that, the second telecommunication interface DIPS initiates theresumption of the data link by a “RESUME” command on the C_(f) channel.This will be acknowledged on the C_(f) channel by the firsttelecommunication interface DIFS. The two telecommunication interfacesDIFS, DIPS then continue the transmission on the C_(f) channel.

C_(f) channel—C_(s) channel according to FIG. 8

The channels are switched back when the first queue WSD and the thirdqueue WSF on both sides are empty and the last I frame has beenacknowledged.

A distinction is made between two cases:

The condition is met first in the case of the telecommunicationinterface which has initiated the switch-over (the secondtelecommunication interface DIPS).

the second telecommunication interface DIPS sends the “SUSPEND” commandon the C_(f) channel.

the first telecommunication interface DIFS rejects the “SUSPEND” commandon the C_(f) channel and continues to transmit information on the C_(f)channel.

thereafter, the first telecommunication interface DIFS will thus alsotake over the initiative for switch-over to the C_(s) channel and, inturn, initiates the “suspension/resumption” when the C_(f) channel is nolonger needed. In the meantime, the second telecommunication interfaceDIPS could also spontaneously use the C_(s) channel again if it needs todo so.

The condition in the case of the telecommunication interface DIFS, DIPS,which has previously caused or retained the switch-over to the C_(f)channel is met later.

This case ends the use of the C_(f) channel and switches back to theC_(f) channel.

In this case, the answering telecommunication interface DIFS, DIPSaccepts the “suspension” on the C_(f) channel. The suspendingtelecommunication interface DIFS, DIPS then initiates the “resumption”on the C_(s) channel.

b) Switch-over within I frames

This approach avoids the additional overheads for optimum DLC frames butpresupposes that the C_(s) channel—C_(f) channel switch-over is gaplessfor the DLC layer and the precise point of switch-over is alsodetectable by the receiver.

The DLC layer in the transmitting section presets a frame length L afterthe start of a frame in the second queue WSS but must expect that itwill necessary to switch over to the third queue WSF within the frameand that the frame will there be terminated in the B-field format. Forthis case, it stores L and all data already transferred to the secondqueue WSS and can use this to form the frame termination (fill octets,check sum) in accordance with B-field rules.

An expansion of the previously standardized functions of the MAC layercan be used for controlling the switch-over which is gapless for the DLClayer. This expansion affects the A-field as follows (see ETS 300 175-3,7.2.5, especially 7.2.5.3 et seq.).

In the MAC message header, one of the code points which is still free isoccupied by the MAC command type “C_(s) channel/C_(f) channelswitch-over”.

The remainder of the A-field essentially contains the followinginformation under this command:

Reference of the MAC connections between which the C_(s) channel/C_(f)channel switch-over is to take place (the already defined ECN (ExchangedConnection Number) will be used).

Specific C_(s) channel—C_(f) channel/C_(f) channel—C_(s) channelswitch-over command.

Acknowledgement: Switch-over accepted/not accepted, confirmation of thecorrect reception of the “acknowledgement” command.

Blank field (use wait function if acknowledgement is not immediatelypossible).

The B-field of the time slots containing these MAC control informationitems either carries user information (U plane) if the C_(s) channel isused, or the signalling information itself or, respectively, noinformation, if the C_(s) channel is used.

In the I frame, the switch-over proceeds in accordance with a similararrangement to that outlined above at point a):

C_(s) channel—C_(f) channel according to FIG. 9

After the MAC connection has been set up for the C_(f) channel, theinitiating telecommunication interface DIFS, DIPS sends, instead of an Iframe segment, the C_(s) channel—C_(f) channel switch-over command onthe C_(s) channel. The other end acknowledges acceptance on the C_(s)channel (there is no reason for rejection in this case). Bothtelecommunication interfaces DIFS, DIPS then continue the transmissionon the C_(f) channel.

C_(f) channel—C_(s) channel according to FIG. 10

When the telecommunication interface DIFS, DIPS initiating the C_(f)channel no longer needs this channel, it sends the C_(f) channel—C_(s)channel switch-over command on the C_(f) channel. If the other end alsono longer needs this channel at this time (WSD, WSF empty), itacknowledges the acceptance of the switch-back. Otherwise, it rejectsthe switch-back and thus, in turn, accepts the initiative for a newactivation of the switch-back if it no longer needs the C_(f) channel.As long as the C_(f) channel is active, it can also be used again by theother end.

Note

Naturally, the method can also be used at I frame boundaries.

There are then two possibilities:

MAC commands and acknowledgements are used, i.e. sent, at DLC frameboundaries.

MAC commands and acknowledgements are preventatively inserted already incurrent transmissions of DLC frames but the time of effectiveness isdefined for DLC frame ends.

This results in the advantage of a gain in time because negotiations andpossible subsequent operations can already take place in parallel withan ongoing transmission.

Miscellaneous

According to DECT rules, the C_(f) channel can be set up by bothtelecommunication interfaces DIFS, DIPS, if needed. Collisions in thiscase should lead to a common channel.

In the case of collision between set-up and clear-down, clear-down haspriority.

The use of the C_(f) channel can also be additionally stimulated byother criteria.

FIGS. 11 to 15 will be used to explain a second illustrative embodimentof the change of channel on the basis of FIG. 6.

FIGS. 11 to 15 show various event/state diagrams which representpossible sequences during the change of channel.

Using FIGS. 1 to 6 as a basis, FIG. 11 shows a first event/state diagramwhich represents the basic control sequence for a change of channel.

The first telecommunication interface DIFS is connected on a firstbearer having a first logical connection number LCNx by a firstsubsystem channel C_(x) to the second telecommunication interface DIPS.In addition, there is a further telecommunication connection between thefirst telecommunication interface DIFS and the second telecommunicationinterface DIPS on a second bearer having a second logical connectionnumber LCNy by a second subsystem channel Cy or, as an alternative, afurther telecommunication connection can be set up between the firsttelecommunication interface DIFS and the second telecommunicationinterface DIPS on a second bearer having a second logical connectionnumber LCNy by a second subsystem channel C_(y).

In this arrangement, the relation LCNx≢LNCy applies to the logicalconnection numbers LCNx, LCNy. The first subsystem channel C_(x) can beconstructed as DECT-specific C_(f) channel or C_(s) channel. Due to thechannel constellations occurring in the DECT-specific telecommunicationsubsystem WLL/RLL, the second subsystem channel C_(y) is accordingly aC_(s) channel or respectively a C_(f) channel or C_(s) channel.According to FIG. 11, the first subsystem channel C_(x) is used fortransmitting information on the C plane.

To set up a bearer, a DECT-specific first B-field message“BEARER_REQUEST” (compare ETSI Publication ETS 300175-3, October 1992,Section 7.3.3.2) is sent as COMMAND and a DECT-specific second B-fieldmessage “BEARER_CONFIRM” (compare ETSI Publication ETS 300175-3, October1992, Section 7.3.3.3) is sent as RESPONSE (compare ETSI Publication ETS300175-3, October 1992, Section 10.5.1.1 to 10.5.1.3) in familiarmanner. Transmission of the first B-field message “BEARER_REQUEST” ispreferably initiated by the second telecommunication interface DIPS inthis arrangement (compare FIGS. 9 and 10 and ETSI Publication ETS300175-3, October 1992, Section 10.5.1.2 and 10.5.1.3).

As a result of the analysis of the ISDN “layer 2/layer 3” messages or,respectively, the amount of information transmitted by these messages(compare printed document “Nachrichtentechnik Elektronik, Berlin 41, P2:(1991) Vol. 4, pages 138 to 143”) on the “ISDN network—ISDN subscriber(Terminal Endpoint TE) transmission link, the first telecommunicationinterface DIFS, for example, recognizes the necessity of initiating achange of channel (change from the first subsystem channel C_(x) to thesecond subsystem channel C_(y)). In this arrangement, the result of theanalysis forms the stimulus for the change of channel.

A possible first result of this analysis can, for example, consist in nomessages being transmitted between the first telecommunication interfaceDIFS and the second telecommunication interface DIPS on the firstsubsystem channel C_(x), preferably for a predetermined period of time.

A possible second result of this analysis can, for example, consist intwo bearers having been set up with in each case one C plane and one Uplane and the bearer, on which the C plane is being used, having to becleared down; so that, accordingly, a change from the previously activeC_(s) channel to be cleared down to the previously inactive C_(s)channel becomes necessary.

To minimize the complexity, it is appropriate to concentrate theanalysis described above in one of the telecommunication interfacesDIFS, DIPS—e.g. advantageously the first telecommunication interfaceDIFS and to control the second telecommunication interface DIPS fromthere [MASTER-SLAVE configuration, in which the first telecommunicationinterface DIFS is the MASTER and the second telecommunication interfaceDIPS is the SLAVE]. In this constellation, the first telecommunicationinterface DIFS always has the possibility of selecting a DECT channelstructure corresponding to the ISDN service (C plane and/or U plane).

Instead of the first telecommunication interface DIFS, the secondtelecommunication interface DIPS can also be provided for this purpose.However, this only works if the latter has direct access to the ISDNlayer 3. The second telecommunication interface DIPS is not capable ofunambiguously mapping, in all situations, a TE-individual connectionwith C plane and U plane onto a corresponding DECT channel structurefrom the ISDN layer 2 function alone.

In the further explanation of the illustrative embodiment, theMASTER-SLAVE configuration described above is used as a basis.

After the first telecommunication interface DIFS has recognized anecessity of a change of channel, it will preferably confirm (answer)all unconfirmed (unanswered) information transmitted and completelyreceived on the first subsystem channel C_(x) in accordance with theHDLC (High level Data Link Control) protocol, the so-called I frames(information packet) with a DECT-specific first DLC message“RECEIVE_READY” sent as RESPONSE (compare ETSI Publication ETS 300175-4,October 1992, Section 7.11.2), if no further I frame is sent.

In accordance with the HDLC protocol, it is possible, for example, totransmit the information (I frames) in transmission sequences (windows)and to acknowledge each transmission sequence (each window) separately.In the present case, for example, the information is transmitted with awindow size of k=3 before an acknowledgement is made. The window sizek=3 signifies with respect to the abovementioned I frames that anacknowledgement of the three frames transmitted previously is made aftereach third I frame. In general, the following relation applies to thewindow size k:

1≦k≦5 n where nεN

Due to the transmission of a first message “SWITCHING_REQUEST”, which,for example, can either be defined in the DECT standard (compare MACmessage “ATTRIBUTES_T._REQUEST” in FIGS. 12 to 15 according to ETSIPublication ETS 300175-3, October 1992, Section 7.2.5.3.8) or is stillto be defined in the latter, the wish by the first telecommunicationinterface DIFS to transfer the transmission of the system informationfrom the first subsystem channel C_(x) to the second subsystem channelC_(y), is conveyed to the second telecommunication interface DIPS. Asalready mentioned, the wish can have arisen due to stimulation orwithout any trigger.

As a result of the transmission of this message, the firsttelecommunication interface DIFS can either—preferably—interrupt its owninformation transmission on the C plane or continue the transmission ofthe information on the C plane. Interruption means that the firsttelecommunication interface DIFS will send no further information for apredetermined period of time. The interruption can occur, for example,before, on or after the transmission of the message.

In addition, the message can be sent at the I frame boundaries andwithin one I frame.

On or after receipt of the message “SWITCHING_REQUEST”, the secondtelecommunication interface DIPS will preferably delete all I framesincompletely received and it can either interrupt or continue its owninformation transmission on the C plane like the first telecommunicationinterface DIFS, on or after receipt of the message “SWITCHING_REQUEST”.

In addition, the second telecommunication interface DIPS can confirm(answer) all unconfirmed (unanswered) information items transmitted onthe first subsystem channel C_(x) in accordance with the HDLC (Highlevel Data Link Control) protocol and completely received, the so-calledI frames, with the DECT-specific first DLC message “RECEIVE_READY” sentas response (compare ETSI Publication ETS 300175-4, October 1992,Section 7.11.2) if its own transmitter is idle.

As an alternative to the direct interruption, it is also possible forthe second telecommunication interface DIPS to conclude the transmissionof an I frame before the interruption.

The interruption of the information transmission or the continuance ofthe information transmission on the first subsystem channel C_(x) by thesecond telecommunication interface DIPS preferably occurs between thereceipt of the first message and before the transmission of a secondmessage “SWITCHING_CONFIRM”, which, for example, can either be definedin the DECT standard (compare MAC message “ATTRIBUTES_T._CONFIRM” inFIGS. 12 to 15 according to ETSI Publication ETS 300175-3, October 1992,Section 7.2.5.3.8) or is still to be defined in the latter.

The second message “SWITCHING_CONFIRM” meets, for example, the requestof the first telecommunication interface DIFS for a change of subsystemchannel by confirming (positively answering) it.

However, it is also possible that the second telecommunication interfaceDIPS either deliberately or unintentionally (e.g. due to the fact thatit has not received the first message due to a fault in the radiotransmission link) does not meet the request.

In the case where the request is deliberately not met, the first message“SWITCHING_REQUEST” will thus be rejected (answered negatively) eitherdirectly or indirectly, e.g. by exceeding a predetermined period of timefor confirming the first message, via the second telecommunicationinterface DIPS.

In the second case, the first message “SWITCHING_REQUEST” will berejected (answered negatively) indirectly, e.g. by exceeding apredetermined period of time for confirming the first message.

In both the abovementioned cases, either the first message“SWITCHING_REQUEST” is retransmitted a predetermined number of times viathe first telecommunication interface DIFS or the change of channel isaborted for an undetermined time.

The result of the transmission of the second message “SWITCHING_CONFIRM”is that the transmission of information is continued on the secondsubsystem channel C_(y). Continuance can preferably take place on orafter transmission of the message.

After or on receipt of the second message “SWITCHING_CONFIRM”, the firsttelecommunication interface DIFS will preferably also delete theunconfirmed information transmitted on the first subsystem channel C_(x)and incompletely received.

Before the information deleted by the first telecommunication interfaceDIFS and the second telecommunication interface DIPS is retransmitted onthe second subsystem channel C_(y), subsystem-specific parameters suchas, for example, the backward transmission counter or timer specific tothe DLC layer (compare ETSI Publication ETS 300175-4, October 1992,Section 9.2.5.7) and the C_(T) packet number (compare ETSI PublicationETS 300175-3, October 1992, Section 7.1.2) are reset.

In addition, a test message which must be confirmed can be transmittedon the second subsystem channel C_(y) before the information deleted bythe first telecommunication interface DIFS and the secondtelecommunication interface DIPS is retransmitted. The test message ispreferably the first DLC message “RECEIVE_READY” (compare ETSIPublication ETS 300175-4, October 1992, Section 7.11.2) sent as commandwhereas the confirmation of the test message is preferably the first DLCmessage “RECEIVE_READY” (compare ETSI Publication ETS 300175-4, October1992, Section 7.11.2) sent as response.

Both the test message and the deleted information are preferablytransmitted with the smallest possible window size according to the HDLCprotocol, i.e. k=1, at the beginning (start phase of the transmission)in order to achieve rapid synchronization on the second subsystemchannel C_(y), and are then transmitted again with the window size k=3.

FIG. 12 shows a second event/state diagram based on FIG. 11, which showsthe control sequence for changing from a first subsystem channel C_(f)to a second subsystem channel C_(s).

The first subsystem channel C_(f) is used for transmitting informationon the C plane. The second subsystem channel C_(s) is not used fortransmitting information on the C plane. However, the U plane isutilized. The first subsystem channel C_(f) has a higher transmissioncapacity than the second subsystem channel C_(s).

The first telecommunication interface DIFS detects that the firstsubsystem channel C_(f) is no longer necessary and sends a first MACmessage “ATTRIBUTES_T._REQUEST” (compare ETSI Publication ETS 300175-3,October 1992, Section 7.2.5.3.8) to the second telecommunicationinterface DIPS.

The second telecommunication interface DIPS confirms the first MACmessage “ATTRIBUTES_T._REQUEST” by sending a second MAC message“ATTRIBUTES_T._CONFIRM” to the first telecommunication interface DIFS.After that, the second subsystem channel C_(s) is used for transmittinginformation on the C plane and the first subsystem channel C_(f) iscleared by transmitting a third MAC message “RELEASE” (compare ETSIPublication ETS 300175-3, October 1992, Section 7.2.5.3.13).

FIG. 13 shows a third event/state diagram based on FIG. 11, whichillustrates the control sequence for changing from the second subsystemchannel C_(s) to a third subsystem channel C_(s).

The second subsystem C_(s) is used for transmitting information on the Cplane. In addition, the U plane is utilized. The third subsystem channelC_(s) is not used for transmitting information on the C plane but the Uplane is utilised. The second subsystem channel C_(s) has the sametransmission capacity as the third subsystem channel C_(s).

The first telecommunication interface DIFS detects that the secondsubsystem channel C_(s) is no longer necessary and sends the first MACmessage “ATTRIBUTES_T._REQUEST” (compare ETSI Publication ETS 300175-3,October 1992, Section 7.2.5.3.8) to the second telecommunicationinterface DIPS.

The second telecommunication interface DIPS confirms the first MACmessage “ATTRIBUTES_T._REQUEST” by sending the second MAC message“ATTRIBUTES_T._CONFIRM” to the first telecommunication interface DIFS.After that, the third subsystem channel C_(s) is used for transmittinginformation on the C plane and the second subsystem channel C_(s) iscleared by transmitting the third MAC message “RELEASE” (compare ETSIPublication ETS 300175-3, October 1992, Section 7.2.5.3.13).

FIG. 14 shows a fourth event/state diagram based on FIG. 11, whichillustrates the control sequence for changing from the second subsystemchannel C_(s) to the first subsystem channel C_(f), the preparation forthe change being initiated by the first telecommunication interfaceDIFS.

The second subsystem channel C_(s) is used for transmitting informationon the C plane. In addition, the U plane is utilized. A bearer having alogical connection number LCN for utilizing the first subsystem channelC_(f) has not yet been set up. The second subsystem channel C_(s) has alower transmission capacity than the first subsystem channel C_(f).

The first telecommunication interface DIFS detects that the firstsubsystem channel C_(f) is needed. However, since there is as yet nobearer having the logical connection number LCN for the first subsystemchannel C_(f), the first telecommunication interface DIFS sends thefirst MAC message “ATTRIBUTES_T._REQUEST” to the secondtelecommunication interface DIPS (compare ETSI Publication ETS 300175-3,October 1992, Section 7.2.5.3.8). It informs the secondtelecommunication interface DIPS with this message of the need for abearer having the logical connection number LCN, e.g. the logicalconnection number LCN0, for the first subsystem channel C_(f).

The logical connection number LCN—in the present case LCN0—is notarbitrarily selected as identification for the bearer to be set up butdeliberately in accordance with a predetermined selection criterion.Formulated generally, this criterion consists in using as logicalconnection number LCN the logical connection number, of the possiblelogical connection numbers LCN0, LCN1, LCN2, which is not yet being usedfor another bearer, that is to say is available.

As an alternative to the abovementioned selection criterion, it is alsopossible to use special features of the selection criterion for issuingthe logical connection number. Thus it is possible—as in the presentcase—always to use, for example, the smallest available number of thelogical connection numbers LCN0, LCN1, LCN2 or the largest availablenumber of the logical connection numbers LCN0, LCN1, LCN2.

The second telecommunication interface DIPS which, according to theexplanations in the description of FIG. 11 is preferably responsible forsetting up a bearer (compare ETSI Publication ETS 300175-3, October1992, Section 10.5.1.2 and 10.5.1.3), sends the DECT-specific firstB-field message “BEARER_REQUEST” (compare ETSI Publication ETS 300175-3,October 1992, Section 7.3.3.2) as command to the first telecommunicationinterface DIFS. After receiving the first B-field message, the firsttelecommunication interface DIFS thereupon sends the DECT-specificsecond B-field message “BEARER_CONFIRM” (compare ETSI Publication ETS300175-3, October 1992, Section 7.3.3.3) as response to the secondtelecommunication interface DIPS. In this state, i.e. after receipt ofthe second B-field message by the second telecommunication interfaceDIPS, the further bearer is set up (compare ETSI Publication ETS300175-3, October 1992, Section 10.5.1.1 to 10.5.1.3).

After that, the first telecommunication interface DIFS sends the firstMAC message “ATTRIBUTES_T._REQUEST” (compare ETSI Publication ETS300175-3, October 1992, Section 7.2.5.3.8) to the secondtelecommunication interface DIPS.

The second telecommunication interface DIPS confirms the first MACmessage “ATTRIBUTES_T._REQUEST” by sending the second MAC message“ATTRIBUTES_T._CONFIRM” to the first telecommunication interface DIFS.After that, the first subsystem channel C_(f) is used for transmittinginformation on the C plane.

FIG. 15 shows a fifth event/state diagram based on FIG. 11, whichillustrates the control sequence for changing from the second subsystemchannel C_(s) to the first subsystem channel C_(f), the preparation forthe change being initiated by the second telecommunication interfaceDIPS.

The second subsystem channel C_(s) is used for transmitting informationon the C plane. In addition, the U plane is utilized. A bearer having alogical connection number LCN for utilizing the first subsystem channelC_(f) has not yet been set up. The second subsystem channel C_(s) has alower transmission capacity than the first subsystem channel C_(f).

The second telecommunication interface DIFS detects that the firstsubsystem channel C_(f) is necessary. However, since there is not yet abearer having the logical connection number LCN, e.g. the logicalconnection number LCN0, for the first subsystem channel C_(f), it setsup the latter.

The logical connection number LCN—in the present case LCN0-is notarbitrarily selected as identification for the bearer to be set up butagain deliberately in accordance with a predetermined selectioncriteria. Formulated, generally, this criterion consists in using aslogical connection number LCN the logical connection number, of thepossible logical connection numbers LCN0, LCN1, LCN2, which is not yetbeing used for another bearer, that is to say is available.

As an alternative to the abovementioned selection criterion, it is alsopossible to use special features of the selection criterion for issuingthe logical connection number. Thus it is possible—as in the presentcase—always to use, for example, the smallest available number of thelogical connection numbers LCN0, LCN1, LCN2 or the largest availablenumber of the logical connection numbers LCN0, LCN1, LCN2.

To set up the bearer, the second telecommunication interface DIPS, whichis preferably responsible for setting up a bearer in accordance with theexplanations in the description of FIG. 11, (compare ETSI PublicationETS 300175-3, October 1992, Section 10.5.1.2 and 10.5.1.3) sends theDECT-specific first B-field message “BEARER_REQUEST” (compare ETSIPublication ETS 300175-3, October 1992, Section 7.3.3.2) as command tothe first telecommunication interface DIFS.

After having received the first B-field message, the firsttelecommunication interface DIFS thereupon sends the DECT-specificsecond B-field message “BEARER_CONFIRM” (compare ETSI Publication ETS300175-3, October 1992, Section 7.3.3.3) as response to the secondtelecommunication interface DIPS. In this state, i.e. after receipt ofthe second B-field message by the second telecommunication interfaceDIPS, the further bearer is set up (compare ETSI Publication ETS300175-3, October 1992, Section 10.5.1.1 to 10.5.1.3).

This is detected by the first telecommunication interface DIFS so thatthe latter sends the first MAC message “ATTRIBUTES_T._REQUEST” (compareETSI Publication ETS 300175-3, October 1992, Section 7.2.5.3.8) to thesecond telecommunication interface DIPS.

The second telecommunication interface DIPS confirms the first MACmessage “ATTRIBUTES_T._REQUEST” by sending the second MAC message“ATTRIBUTES_T._CONFIRM” to the first telecommunication interface DIFS.After that, the first subsystem channel C_(f) is used for transmittinginformation on the C plane.

The invention is not limited to the particular details of the methoddepicted and other modifications and applications are contemplated.Certain other changes may be made in the above described method withoutdeparting from the true spirit and scope of the invention hereininvolved. It is intended, therefor, that the subject matter in the abovedepiction shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:
 1. (Amended) A method for allocatingtelecommunication channels of different channel capacity in a hybridtelecommunication system, comprising the steps of: a) providing in thehybrid telecommunication system, for the transmission of systemmessages, a1) a first telecommunication subsystem having a firsttelecommunication channel and a first information transmission capacity,and a2) a second telecommunication subsystem having a secondtelecommunication channel and a second information transmission capacityand having a third telecommunication channel and a third informationtransmission capacity; b) providing in the second telecommunicationsubsystem, for transmitting the system messages and for transmittingsubsystem messages of the second telecommunication subsystem, a firsttelecommunication interface and a second telecommunication interfacewhich are connected to one another via at least one of the secondtelecommunication channel and the third telecommunication channel; c)tying the second telecommunication subsystem, as local informationtransmission loop, into the first telecommunication subsystem via thefirst and second telecommunication interfaces; d) providing that thefirst information transmission capacity is lower than the secondinformation transmission capacity and higher than the third informationtransmission capacity; e) transmitting system messages, when an amountof information to be transmitted on the first telecommunication channeldoes not exceed an amount of information that is transmittable on thethird telecommunication channel, via the first telecommunication channeland the third telecommunication channel; and f) transmitting systemmessages when an amount of information to be transmitted on the firsttelecommunication channel exceeds an amount of information which istransmittable on the third telecommunication channel, via the firsttelecommunication channel and the second telecommunication channel. 2.The method according to claim 1, wherein the transmission of the systemmessages in the second telecommunication subsystem is controlled suchthat a) the system messages are placed in a queue in the firsttelecommunication interface serving as message transmitting device, b) aloading ratio of the queue filled with the system messages isdetermined, c) the third telecommunication channel is stimulated fortransmitting the system messages when the loading ratio does not exceeda threshold value, d) the second telecommunication channel is stimulatedfor transmitting the system messages when the loading ratio exceeds thethreshold value.
 3. The method according to claim 2, wherein a change ofchannel from the second telecommunication channel to the thirdtelecommunication channel is initiated when there are no system messagesin the queue.
 4. The method according to claim 1, wherein a) themessages are transmitted on one of the second telecommunication channelor the third telecommunication channel, b) a switch-over command istransmitted by which one of the first and second telecommunicationinterfaces signals to the other telecommunication interface that themessages are to be transmitted on the third telecommunication channelor, respectively, the second telecommunication channel, c) a switch-overresponse is transmitted by the telecommunication interface receiving theswitch-over command to the telecommunication interface sending theswitch-over command.
 5. The method according to claim 4, wherein theswitch-over command is retransmitted if the switch-over response is nottransmitted after a predetermined period of time.
 6. The methodaccording to claim 5, wherein, when the switch-over response fails toappear repeatedly, the transmission of the switch-over command iscontinued for a predetermined number of times before control of thechange of channel is aborted for an indeterminate time.
 7. The methodaccording to claim 4, wherein the switch-over response is a switch-overconfirmation by which the telecommunication interface receiving theswitch-over command signals to the telecommunication interface sendingthe switch-over command that the information is transmitted on the thirdtelecommunication channel or, respectively, the second telecommunicationchannel.
 8. The method according to claim 4, wherein the transmission ofthe messages is interrupted before, on or after the transmission of theswitch-over command and wherein the transmission of the messages isresumed on or after the transmission of the switch-over response.
 9. Themethod according to claim 8, wherein the transmission of the messages isinterrupted immediately after the transmission of the switch-overcommand and wherein the switch-over response is transmittedsubstantially immediately after the transmission of the switch-overcommand.
 10. The method according to claim 8, wherein the transmissionof the messages is interrupted by the telecommunication interfacesending the switch-over command immediately after the transmission ofthe switch-over command, wherein the transmission of the messages isinterrupted by the telecommunication interface receiving the switch-overcommand substantially immediately after the transmission of theswitch-over command when an integral message packet has been terminallytransmitted by the telecommunication interface receiving the switch-overcommand and wherein the switch-over response is transmittedsubstantially immediately after the transmission of the informationpacket.
 11. The method according to claim 8, wherein the transmission ofthe messages is interrupted by the telecommunication interface sendingthe switch-over command immediately after the transmission of theswitch-over command, wherein the transmission of the messages isinterrupted by the telecommunication interface receiving the switch-overcommand after a predetermined period of time, to confirm messagesalready received, substantially immediately after the transmission ofthe switchover command, and wherein the switch-over response istransmitted substantially immediately after the transmission of theconfirmation.
 12. The method according to claim 8, wherein aninformation packet of the information to be transmitted, which has beenincompletely transmitted or is unanswered due to the direct interruptionis retransmitted on the third telecommunication channel or,respectively, the second telecommunication channel after a change ofchannel.
 13. The method according to claim 4, wherein predeterminedsubsystem-specific parameters are reset after the transmission of theswitch-over response and before the transmission of the system messageson the third telecommunication channel or, respectively the secondtelecommunication channel.
 14. The method according to claim 4, whereina test message with a request for confirmation is sent on the thirdtelecommunication channel or, respectively, the second telecommunicationchannel after a change of channel.
 15. The method according to claim 14,wherein the test message is a RECEIVE_READY message which is sent as acommand and that the confirmation is a RECEIVE_READY message which issent as a response.
 16. The method according to claim 4, wherein themessages are transmitted in accordance with a predetermined principle oftransmission with a predetermined window and wherein the messages aretransmitted with a smallest possible window on the thirdtelecommunication channel or, respectively, the second telecommunicationchannel after a change of channel.
 17. The method according to claim 16,wherein the principle of transmission with the predetermined window isan HDLC protocol for transmitting HDLC frames.
 18. The method accordingto claim 4, wherein system messages with at least one of userinformation, the system information and the subsystem information aretransmitted on bearers having different logical connection numbersbetween the first and second telecommunication interfaces of thetelecommunication subsystem.
 19. The method according to claim 18,wherein a first logical connection number, which is not occupied byother bearers, is allocated to a first bearer to which the secondtelecommunication channel is allocated.
 20. The method according toclaim 19, wherein the first logical connection number is a smallestissuable logical connection number of logical connection numbersidentifying the bearers.
 21. The method according to claim 19, whereinthe first logical connection number is a largest issuable logicalconnection number of the logical connection numbers identifying thebearers.
 22. The method according to claim 4, wherein the switch-overcommand is transmitted by the first telecommunication interface.
 23. Themethod according to claim 4, wherein at least one of the switchovercommand and the switch-over response is acknowledged by a respectivetelecommunication interface receiving the switch-over command or,respectively, the switch-over response.
 24. The method according toclaim 23, wherein at least one the switch-over command and theswitch-over response is acknowledged in one of a rejecting or acceptingmanner.
 25. The method according to claim 23, wherein, when theswitch-over command or, respectively, the switch-over response isrejected, the telecommunication interface signaling the respectiverejection change of channel with the transmission of the switch-overcommand.
 26. The method according to claim 4, wherein, when theswitch-over command and the switch-over response are accepted, aftertransmission resumes, transmission of the messages starts at a pointwhere transmission has been interrupted.
 27. The method according toclaim 4, wherein the switch-over command is transmitted by one of thefirst telecommunication interface or the second telecommunicationinterface.
 28. The method according to claim 4, wherein the switch-overcommand and the switch-over response are transmitted in a firstinformation transmission layer of an information transmission structuredivided into information transmission layers of the telecommunicationinterface, in which substantially the subsystem messages aretransmitted.
 29. The method according to claim 28, wherein the firstinformation transmission layer is a DLC layer of a DECT standard. 30.The method according to claim 4, wherein the switch-over command and theswitch-over response are transmitted in a second informationtransmission layer which, with respect to an information transmissionstructure divided into information transmission layers of thetelecommunication interface is subordinate to a first informationtransmission layer substantially provided for transmission of thesubsystem messages, and wherein the switch-over command and theswitch-over response are transmitted in this arrangement such that adata structure of the first information transmission layer remainsunimpaired.
 31. The method according to claim 30, wherein the secondinformation transmission layer is a MAC layer of a DECT standard. 32.The method according to claim 4, wherein the switch-over command is anATTRIBUTE_REQUEST information element of a DECT standard.
 33. The methodaccording to claim 4, wherein the switch-over response is anATTRIBUTE_CONFIRM information element of a DECT standard.
 34. The methodaccording to claim 4, wherein the switch-over command is a SUSPENDinformation element of a DECT standard.
 35. The method according toclaim 4, wherein the switch-over command is a RESUME information elementof a DECT standard.
 36. The method according to claim 1, wherein thefirst telecommunication subsystem is an ISDN system.
 37. The methodaccording to claim 36, wherein the system messages are transmitted on aD channel.
 38. The method according to claim 1, wherein the secondtelecommunication subsystem contains a DECT/GAP system.
 39. The methodaccording to claim 38, wherein the first telecommunication interface isa DECT INTERMEDIATE FIXED SYSTEM and the second telecommunicationinterface is a DECT INTERMEDIATE PORTABLE SYSTEM.
 40. The methodaccording to claim 38, wherein the second telecommunication channel is aC_(f) channel of the DECT system.
 41. The method according to claim 38,wherein the third telecommunication channel is a C_(s) channel of theDECT system.
 42. The method according to claim 32, wherein theswitch-over command is an ATTRIBUTE_REQUEST information element of theDECT standard.
 43. The method according to claim 38, wherein theswitch-over response is an ATTRIBUTE_CONFIRM information element of theDECT standard.
 44. The method according to claim 38, wherein theswitch-over command is a SUSPEND information element of the DECTstandard.
 45. The method according to claim 38, wherein the switch-overresponse is a RESUME information element of the DECT standard.
 46. Themethod according to claim 1, wherein the second telecommunicationsubsystem contains a GSM system.
 47. The method according to claim 1,wherein the second telecommunication subsystem contains one of a PHSsystem, a WACS system or a PACS system.
 48. The method according toclaim 1, wherein the second telecommunication subsystem contains one ofa “IS-54” system, or a PDC system.
 49. The method according to claim 1,wherein the second telecommunication subsystem contains one of a CDMAsystem, a TDMA system, a FDMA system or a system which is hybrid withrespect to the CDMA system, the TDMA system, and the FDMA system,ttransmission standards.